The ever increasing sophistication and logic speed of computers have made these devices extremely sensitive to power-line disturbances. Line-voltage spikes and noise cause not only physical damage, but also frequent loss of data and irreplaceable information. Numerous attempts have been made to develop various types of protectors to prevent damaging electrical noise from interfering with the computer operation Such devices are generally known as Line Conditioners or Filters. These devices may be grouped into two categories of active and passive circuits.
The passive circuits are essentially filter networks, which may include some form of surge protector and which have no components to alter the basic shape of the incoming line-voltage sine wave. On the other hand, the line conditioners with active circuits include some form of voltage regulator that can maintain the output voltage within reasonable limits under extreme high or low line-input conditions. The active circuits in the line conditioners range from ferro-resonant devices to many types of tap-switching, multi-primary switching, switch-mode synthesizers and energy dispensers. All of these devices are well-known in the art. However, all of these devices utilize circuits to either maintain or to restore an almost perfect sine wave, and their quality is not only judged by their regulation response time, noise rejection, and efficiency, but also by the quality of the output sine wave, i.e., minimum distortion and harmonic content.
The general assumption is that most electrical equipment was designed to operate on the line-voltage sine wave, and that only a sine wave can provide dependable operation. This assumption, however, can be incorrect; and when it is, this causes a great deal of energy to be wasted in electronic equipment in the form of heat, which also causes great electrical stresses on components so that their life is shortened.
The conventional approach in electronic equipment design is to provide a reliable operating margin that is based on certain standards of utility companies, with some additional margin to allow for power losses that occur in wiring inside the buildings. The typical input voltage design parameters are +/-10% from some average level. In the United States, it is common to use 115 V as average, although the U.S. nominal voltage is actually 120 V. However, the U.S. standard is 120 V +6%/-14%, and this yields an average of 115 V.
In all electronic equipment, especially computers, virtually all of the AC-input power is converted into DC by power supplies. Regardless of configuration, with or without power transformers, all power supplies utilize peak rectifiers that conduct current only during the very peak portion of the input sine wave in order to charge energy into the storage capacitors ad to recharge those capacitors repetitively during every half cycle peak. As soon as the sine wave has passed beyond each peak, the rectifier diodes become reverse-biased and do not conduct again until the sine wave approaches the peak of the next following halfcycle. During the time interval between the sine-wave peaks, the power supplies draw DC energy out of the storage capacitors so that the DC-voltage across these storage capacitors decreases gradually during the discharge time intervals. The DC-voltage waveform across storage capacitors has a characteristic waveform of charge and discharge periods, called "ripple ".
The DC-power supplies in electronic equipment are designed so that their regulator circuits still have sufficient operating margin (compliance voltage) at the very end of each discharge period under the absolute worst case conditions. The worst case condition is when the input line-voltage happens to be very low, 103 V in the United States. Thus, since the rectifiers operate only during the peak of the sine wave, the actual design criteria is not 103 V rms, but its equivalent peak voltage of 145.6 V pk (103 .times.1.414 =145.6).
When the input line-voltage is above this low limit, it causes the DC-voltage on the storage capacitors to increase with a resultant increase in compliance voltage in the DC power supplies. If the power supplies have conventional linear pass regulators, this causes the excess voltage to be absorbed by the regulators, and this excess power is converted (wasted) into heat. The worst case energy waste occurs when the line-voltage is at the extreme high condition of 127 V rms, i.e., 179.5 V peak. This is an increase of 33.9 V of the peak level above the minimum required 145.6 V , amounting to a waste of energy of 23.3%.
One might now conclude that since electronic equipment uses peak rectifiers, it would be advantageous to supply a square wave as a power input. A square wave would achieve essentially continuous conduction of the rectifiers because there is a flat top from start to finish of each half cycle. This would eliminate the ripple voltage, reduce the power supply compliance stress, and greatly improve the system's efficiency. Unfortunately, as shown earlier, the minimum peak voltage (flat top) would have to be about 140 V in order to provide adequate compliance voltage for proper power supply operation. Since there would be no charge/discharge ripple, the square-wave peak can be somewhat lower than the sinusoidal peak of 145.6 V. However the rms value of a square wave is equal to its peak value, i e., a square wave of 140 V peak is also 140 V rms.
Since the electrical equipment was not designed to operate on 140 V rms, all magnetic components (such as transformers, relays, and fans) would saturate and cause malfunction and damage. In addition, the fast-rising wave fronts of a square wave can cause high-frequency noise problems, which is objectionable. The calculations and conclusions of the preceding paragraphs represent the technology and common knowledge of prior art as it is taught today.